Chamfering

[saltedplug]

Thanks to all for your responses, especially sasquatch.
The tenon chamfer makes sense but not the mortise. I can readily see the mortise chamfer managing condensate as smoke navigates a smaller diameter as it enters the tenon, but the mortise chamfer is another matter. It must manage the smoke that escapes the tenon and travels down its sides, although how this could happen given the draw is a mystery. So this chamfer allows the condensate to be stepped down before escaping at the point of the mortise/tenon junction, preventing condensation at this point?

 

[sasquatch]

The only chamfer in the mortise is simply cause by the drill bit being angled (if it's a fluted/twist bit). If a guy cuts the mortise with a forstner, it's dead flat on the bottom. In either case, no smoke goes anywhere "past" the tenon, it all goes up the aiway in the stem +- however much it swirls around in whatever space is left between the tenon and the mortise bottom.

 

[saltedplug]

So you're saying what looks to be a chamfer is not a chamfer, and that in any case no smoke escapes being drawn into the tenon, and that the chamfer is an aftereffect of the drill?

 

[sasquatch]

Unless I am totally mis-understanding you, then, yes, that is what I am saying.

 

[balkisobrains]

I was reading a little bit about this, and they were saying not to worry about it if the faces are flat and there is no space between them, and presuming that the airways match up. If there is a space, they were saying that you could try chamfering the tenon on the stem, regardless of the shape of the mortise. I think that they were talking about chamfering that too, but I don't remember. I tried this on one of my pipes tenons where there was a space, just to do it. I bought two types of wood countersink bits, piloted and "free", and the cutting blades all basically stunk at cutting the acrylic manually, so I put my drill vertically in a vice and did it carefully "by hand" that way. The blades didn't really want to cut easily then either, so I don't know if the acrylic was a type that is very hard, or what. But I managed not to melt anything, and I stopped cutting right before the original edge.

 

[saltedplug]

Thanks!

 

[zack24]

they were saying not to worry about it if the faces are flat and there is no space between them, and presuming that the airways match up

You actually need a space between the bottom of mortise and end of tenon...Imagine a tenon fitting perfectly flush against the bottom of the mortise...Now give it a few years of gunk and swelling from moisture...you're left with a gap between the shoulder of the stem and the shank. That's why everyone leaves a slight gap between the two...
I'm a big fan of using a chucking reamer to leave a flat bottomed mortise- I use lot of Delrin tenons and find when drilling different materials like morta and briar, the same drill will create a hole that varies just enough in size to screw up the fit...Much easier to drill them slightly undersize and then go to the final diameter with the chucking reamer which are sized in .0005" increments

 

[crashthegrey]

I find that chamfering the tenon helps with airflow into the stem. I do it to the pipes that I make, but I don't judge someone for disagreeing with me.

 

[balkisobrains]

Here is one of my pipes that I enlarged the airway on, but I want to say that it came chamfered brand-new.

Here is the one that I chamfered. Originally, the end of the tenon was actually slightly convex, like a hemisphere with a hole for the airway.

These are the bits that I used. I mis-remembered my story a little bit. I bought one set of these and a different tool for something else that day. Anyway, these have movable/removable pilot bits, and I used them with and without the bits. The chamfer blades did not seem to cut very well manually by hand, or with my hand drill/vice combo either.

 

[snagstangl]

I use a countersink hand tool when I chamfer a stem.

 

[balkisobrains]

I might try to sharpen mine, because I want to be able to use them with a hand-powered ratcheting screwdriver handle.

 

[halfy]

Theoretically chamfer should help in a smooth airflow, particularly for bent pipes in which the stem air way is not co-linear with that in the shank, the chamfer creats a shorter path of airflow.
Anyway, chamfer is not always a must in real applications. There is a "none-slip boundary condition" for fluid flows in most cases...in another word, the air close to the airway wall barely moves. Though some pipes whistle, they still smoke perfect :P
I sometimes chamfer the tenon of my bent dunhills. They never do that...and I like that arrogance.

 

[fnord]

I sometimes chamfer the tenon of my bent dunhills. They never do that...and I like that arrogance.

LOL
:clap: :clap: :clap:

 

[craiginthecorn]

What I don't understand is, what's the value of a 4mm draft hole in the briar if the stem narrows to 3mm before the smoke exits? Why not 3mm the whole way? My best smoker among many fine pipes has a 4mm drilling and it's easy to see that it's the same diameter from the bowl to the chamfer a the button. Coincidence? I think not.

 

[saltedplug]

J. T. Cooke purportedly keeps the same area airway from chamber draft to bit. But because of the narrowing at the tenon, which by fiction adheres to the walls of the airway, just past the bottom of the mortise-if I have the lingo correct-the tenon constricts the airway. Depending on the diameter of the tenon there is a greater or lesser variance. Past that there need not be any changes, yet as the smoke flows through the stem and bit, the shape will vary.
This airway would seem the most simple and elegant. There are terms from physics that describe the passage of smoke through the airway, such as turbulence, but an airway of the same area throughout would seem to be the simplest, and perhaps the best.

 

[zack24]

Guys, visualize this- 5/32" or 4mm straight drill on the shank. 5/32" or 4mm tapered drill to within .75" of the button. At the button, using drill bit and files, create a nice fan shape funnel going up 1.25" into the stem. What you're left with is a nice open round draft that gradually morphs into a wide thin funnel....but the cross section volume is the same...When that is done- do the Harris test- double a pipe cleaner and stick it through from button to bowl- if it passes, that's an open draw......

 

[saltedplug]

So until .75" of the bit the airway is of the same diameter. But at the tenon it constricts and then reverts to the size of the shank airway. Most of the discussion so far in regard to the tenon chamfer has been about it reducing condensation at the tenon tip. But if we are talking keeping the airway one size to maintain laminar flow, the tenon introduces turbulence and chamfering is the best strategy for to reduce it.
I know all about these terms from a paragraph in Encyclopedia Britannica:

Turbulent flow, type of fluid (gas or liquid) flow in which the fluid undergoes irregular fluctuations, or mixing, in contrast to laminar flow, in which the fluid moves in smooth paths or layers.

Yet as the smoke flows through the stem and bit, the airway shape will vary. Zack, not that there is a need to do so, but do you see any merit to keeping the same size airway through the stem and bit?
Further, Sasquatch said that pipes that smoke with glory have had the entire airway smoothed by filing. I guess this would increase laminar flow, but if so, I'm not sure how the delivery of flavor would be enhanced by the slight turbulence of less-smooth airway surface. And as Pipestud remarked, the smoke travels so fast down the airway that such speed obviates the slight drop in temperature of the smoke when comparing a 5.5" pipe with a churchwarden, which is to say that I doubt I could tell the difference between a pipe with a smooth as compared to a normal airway. When I draw I get smoke in my mouth.

 

[zack24]

do you see any merit to keeping the same size airway through the stem and bit?

Work with me on this one....If you have a 4mm airway constant to the bit....My normal thickness in the bite zone is 3.8-4mm...so if executed perfectly, a 4mm airway would break through on the top and bottom of the bite zone....You pretty much have to use a tapered bit on the stem,,,
...and on smoothing the airway of the stem...I take a 1' pipe cleaner, stick one end in the vise, Load it up with a jewelers rouge, thread the stem on it, and stroke that sucker back and forth with great enthusiasm. Repeat with a clean pipe cleaner...and you're good...

 

[jpmcwjr]

I've learned more about the interior of pipe stems than I wanted to know. But interesting!
I'm sure I could not tell the difference in drawing on a pipe with a shiny smooth airway and one that wasn't so prepped. And turbulence, schmurbulence! Unless there's a huge chamber through which the smoke passes, I doubt that it matters, either for a good smoke nor increasing moisture. (though the gap can trap the moisture)

 

[saltedplug]

Eureka!...You are sticking the stem in the correct orifice!...

Zack, I guess we all have our day of arrogance; I have had too many on this board. But this isn't funny, and even if I am missing the joke, which is certainly possible, I would request that you never say anything like this to me again. A thousand pardons for my ignorance, but if I don't question, I don't learn. Your attitude is boorish.
Don't ever say anything like this to me again.